A federal district in Missouri has ruled that states that decided to make their residents use the federal health insurance marketplace to buy coverage rather than create a state-run exchange can’t affect how the federal marketplace operates, including limiting navigators, who help people buy insurance.

The preliminary injunction issued Thursday said states can’t impose more requirements or limits on a federal marketplace that they don’t run. The ruling only applies to Missouri.

Earlier this week, the Texas Department of Insurance issued rules for “navigators,” requiring them to complete 20 hours of training beyond that required by the federal government.

Missouri also imposed additional requirements on navigators, including 30 hours of training. If navigators became licensed, they were restricted in what they could do in the performance of their work.

About a dozen states passed laws restricting who could help consumers buy insurance. Some states require licenses or advanced training. Some restricted health clinic employees and volunteers from explaining insurance terms. Others were not allowed to help people compare plan benefits and prices.